The pick-up truck is a kind of extremely utility vehicle; it is not only a manned car but is also a loading truck. However, the car of the pick-up truck is without roof, thus the goods inside are easily in sun scorched and rain drenched. The wind resistance thereof during running is rather higher compared to sedans or light vans. In view of this the car cover of pick-up trucks has been invented. The car cover is of a soft cover, which is hinged with the car and covers the car, accomplishing the result of protecting inside goods and saving consumption of the fuel.
The locking devices are commonly disposed on the bottom of car covers. Those locking devices have different kinds of constitution, among them the dominating ones are mentioned as follows: as shown in FIG. 1, it is a locking device with annular constitution composing a pedestal 1 which is fixed on the car cover, an annular case 2 slips on pedestal 1, the one end of a swing stem 3 is disposed on the annual case 2 in such a way that it can swing back and forth, the other end of the swing stem 3 pierces through a lock hook 4 and is inserted into a swing handle 5. As shown in FIG. 2, it is a locking device with I shaped constitution composing a pedestal 1 with a coulisse 1, the pedestal 1 is fixed on the car cover, a I shaped slider 2 pierces though a coulisse 4 on the pedestal 1, the one end of a swing stem 3 disposed on the bottom of the I shaped slider 2 in such a way that it can swing back and forth, the other end of the swing stem 3 pierces through a lock hook 4 and is inserted into a swing handle 5. As shown in FIG. 3, it is a locking device with coulisse constitution composing a pedestal 1 with a coulisse in middle, a slider 2 is inserted into the coulisse of the pedestal 1, the one end of a swing stem 3 is connected with a “-” character shaped slider 2, the other end of the swing stem 3 pierces through a lock hook 4 and is inserted into a swing handle 5.
Although the locking devices above mentioned can accomplish the result of hinging the car cover on the car for covering, they have a common shortage, i.e. the main body of constitution can only bear insufficient force, and is easily subject to deformation: in the process of locking tight, the mentioned annual case 2, the I shaped slider 2 and the “-”character shaped slider 2 all produce sliding friction. If this kind of friction is too larger, then the operation will be difficult, if this kind of friction is too smaller, then it is easily slipped and cause the locking between the car and car cover insufficiently tight.